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Black packaging gets the green light: colourants make recycling possible

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Nextek is a specialist consulting company providing expertise in the design, optimisation, processing and recycling of polymeric materials.
Previously recyclers had not be able to separate out black plastics from a mixed plastics waste stream and as a result much of it went into landfill or for incineration.
Innovations resulting from the project, led by Nextek, have the potential to create new business for plastics colourant and material suppliers, packing manufacturers and recycling companies while delivering benefits over existing waste management options.
The new black colourants allow NIR spectroscopy to sort black plastic packaging waste, such as pots, tubs and trays, by polymer type so they can be recycled into high quality materials. The colourants work in APET, CPET, PP, HDPE, PS, and PVC materials.
Alan Davey, our Director of Innovation, says: “The new colourants mean that black packaging, such as meat trays, can now be automatically detected and recovered so that they can be used in new applications as substitutes for virgin plastics. Additionally they offer improvements in recycling revenues as well as savings in carbon emissions and landfill volumes.”
There are approximately one million tonnes of rigid mixed plastic packaging in the UK waste stream and black plastic packaging could represent between 3-6% of this volume. Conservative industry estimates indicate that this could be around 26,000 - 30,000 tonnes per annum of black plastic packaging. Estimates from other industry sources suggest that the figure could be as high as 60,000 tonnes per annum.
Carbon black is widely used as a colorant in food contact packaging because it provides a contrasting background and allows the colours of food to stand out. Additionally it is low cost, has good dispersion and masking properties which allows off-cuts of other colours to be mixed together and manufactured into black items.
In large scale manufacturing trials at LINPAC Packaging food contact trays were manufactured with PP, APET and CPET, using either the Colour Tone or the Colour Matrix colourants.
Generally the sheet extrusion was successful and thermoforming operations ran well using standard settings. Initial trials used a 2% addition rate.
Laboratory trials of filling and sealing tray samples were also successful and NIR detectable colourants were found to make no significant difference to the heat required achieving seals.
In large scale sorting trials at Jayplas Plastics virtually all the PP and PET trays (>99%) were correctly identified by the NIR detectors and were successfully sorted.
TITECH, S+S, RTT Unicorn and Pollen, all manufacturers of NIR sorting machines, were also sent samples of trays made with detectable black colourants and found that they were able to sort them by polymer type and colour. The only adjustment necessary was tweaking of the operating software to ensure that a black tray was not misinterpreted as a clear tray against the background of a black conveyor belt.
Alan says: “Implementation of either detectable black colourants or novel sorting technologies at facilities that enable the recovery of black plastic packaging is expected to have significant net environmental benefits over the current situation where black plastics are primarily ending up in landfill. Previous analysis by WRAP has found that approximately 0.6 tonnes of CO2 can be saved for every tonne of mixed plastics mechanically recycled.”

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